1. Field of the Invention
The present invention relates generally to inkjet printers and, more particularly to an inkjet printer maintenance system.
2. Description of the Related Art
Thermal inkjet printers apply ink to a print medium by ejecting small droplets of ink from an array of nozzles located in a printhead of a printhead cartridge. An array of thin-film resistors on an integrated circuit on the printhead selectively generates heat as current is passed through the resistors. The heat causes ink contained within an ink reservoir adjacent to the resistors to boil and be ejected from the array of nozzles associated with the resistor array. A printer controller determines which resistors will be “fired” and the proper firing sequence so that the desired pattern of dots is printed on the medium to form an image.
Replacement printhead cartridges include integrated ink reservoirs. These reservoirs often contain less ink than the printhead is capable of ejecting over its life. The useful lifetime of a printhead cartridge can be extended significantly if the integrated ink reservoir can be refilled. Several methods now exist for supplying additional ink to the printhead after the initial supply in the integrated reservoir has been depleted. Most of these methods involve continuous or intermittent siphoning or pumping of ink from a remote ink source to the print cartridge. The remote ink source is typically housed in a replacement ink tank which is “off-carrier,” meaning it is not mounted on the carriage which moves the printhead cartridge across the print medium. In an off-carrier ink supply system, the ink usually travels from the remote ink tank to the printhead cartridge through a flexible conduit.
When an off-carrier-ink-tank printer is filled or re-filled with ink, air can inadvertently enter the printhead reservoir with the ink. For the printhead to operate properly, this air must be periodically removed. The current approach for removing this air (maintaining the printhead) is to use a vacuum pump to pull ink and air through the printhead manifold. An arrangement having a gear train actuating a cam system is used to open a spring loaded plunger valve for each individual color reservoir to be serviced. One problem with this arrangement is that it is overly complicated just to perform the simple function of opening the valves.
Consequently, there is a need for an innovation that will overcome the problem associated with removing air when filling or re-filling ink in the prior art inkjet printer systems.